1. Field of the Invention
The present invention generally relates to refrigeration systems. More particularly, the present invention relates to apparatuses and methods for defrosting of an evaporator, and especially the evaporator coil, in a refrigeration system.
2. Description of the Related Art
Refrigeration systems are well known in the art and a closed-flow refrigeration system generally includes a compressor, a condenser and condenser fan, a refrigerant tube between the components, an expansion device such as a capillary tube, an evaporator that has an evaporator coil and an evaporator fan, and a thermostatic relay coupled to a power supply to engage the refrigeration system. In operation, the compressor cycles on and off to compress the refrigerant which then passes to the condenser which cools and liquefies the refrigerant and discharges excess heat from the refrigerant environment. The liquid refrigerant then passes to the evaporator and is expanded or vaporized in the evaporator and the expanding refrigerant absorbs the ambient heat of the evaporator such that the evaporator produces cooling, and ambient air is passed thereover by the evaporator fan and a stream of cool air is thus generated.
The cooling of the ambient air passing through the evaporator and around the evaporator coil causes condensate, and subsequently, frost to build up on the evaporator as the refrigeration system operates. Such frost must be removed in order for the evaporator to function properly and have convection with the evaporator adequately cool the ambient air during the refrigeration cycle. In order to minimize frost in the evaporator, most refrigeration systems therefore maintain activation of the evaporator fan to defrost the evaporator and evaporator coil when the refrigeration cycle is not active, i.e. the compressor and condenser are not running and compressed cooled refrigerant is not flowing.
There are other apparatuses and methods known in the art to defrost the evaporator coil in addition to the method of activating the evaporator fan while the refrigeration system otherwise cycles off. A hot gas defrosting system gathers hot gas from the discharge of the compressor and passes it through the evaporator in proximity to the evaporator coil through the use of an additional hot gas line with associated valves and controls. Furthermore, the use of hot gas for defrosting provides a thermal shock to the components of the evaporator that increases wear and necessity of repair of such components.
Electrical heating elements are sometimes provided in, or in proximity to, the evaporator and evaporator coil, or in conjunction with an evaporator fan to provide heat to the evaporator and evaporator coil sufficient for defrosting. The electrical elements, however, are quite inefficient and consume significant power in producing energy. Moreover, the use of electrical elements can also create a thermal shock to the evaporator components and cause deleterious effects similar to the use of a heat gas line.
Another known method of defrosting the evaporator is simply to cycle the compressor off for a sufficient duration to allow the evaporator to warm and the condensate thereupon to drain. However, such method is slow and unpractical for very cold refrigerant temperatures, i.e. far below 32.degree. F., and is impractical for refrigeration systems that must provide a significant amount of refrigeration.
Accordingly, an apparatus and method of defrosting the evaporator and evaporator coil of a refrigeration system that is efficient, simple, and which does not cause a significant thermal shock to the evaporator components during defrosting would represent an improvement over the prior art evaporator defrosting devices and methods.